The present invention relates to a stencil printing machine for sandwiching a print sheet between a printing drum wound with a stencil sheet and a roller to thereby transfer the print sheet and printing the print sheet by supplying ink from an inner portion of the printing drum. Particularly, the present invention relates to a stencil printing machine preventing ink from being leaked from between the printing drum and the stencil sheet in the stencil printing machine.
An explanation will be given of an example of a structure of a conventional stencil printing machine and a problem thereof in reference to FIG. 11 through FIG. 13. As shown by FIG. 11, the stencil printing machine is provided with a printing drum 100 in a shape of a hollow cylinder and an outer roller 101 provided outside of the printing drum 100. The printing drum 100 and the outer roller 101 are arranged by interposing a predetermined interval therebetween and central axes thereof are in parallel with each other.
First, the printing drum 100 is provided with two pieces of side plates arranged to be opposed to each other by interposing a predetermined interval therebetween and one piece of a shaft 103 for coaxially connecting the two side plates 102. The side plates 102 and the shaft 103 are rotatably provided in a frame of the printing machine. The side plates 102 and the shaft 103 are driven to rotate by being connected to driving means, not illustrated.
Outer peripheral faces of the side plates 102 are wound with a flexible peripheral wall 104. One end of the peripheral wall 104 is fixed and placed on the respective side plates 102. The other end thereof is connected by a spring. The peripheral wall 104 is formed with an ink-permeable perforated portion 105 substantially in a rectangular shape. The perforated portion 105 corresponds to a printing area. Further, a surrounding of the perforated portion 105 constitutes a nonperforated portion 109 for preventing ink from permeating therethrough. Although not illustrated, ink supplying means is provided at the inner portion of the printing drum 100. The ink supplying means can supply ink to an inner peripheral face of the printing drum 100. An inner roller 106 is provided at the inner portion of the printing drum 100. The inner roller 106 is attached pivotably to the shaft 103. The inner roller 106 is moved to lift and lower at predetermined timings in synchronism with rotation of the printing drum 100 and presses the peripheral wall 104 to an outer side in printing operation. The peripheral wall 104 pressed by the inner roller 106 is deformed to an outer side against urge force of the spring, mentioned above.
As shown by FIG. 12, a perforated stencil sheet 107 is wound around the outer peripheral face of the peripheral wall 104 of the printing drum 100. The stencil sheet 107 covers all of the perforated portion 105 of the peripheral wall 104. The stencil sheet 107 is of a size covering the nonperforated portion 109 at the surrounding of the perforated portion 105. When the printing drum 100 is rotated, the inner roller 106 is lifted and lowered in synchronism therewith. A print sheet 108 is supplied between the printing drum 100 and the outer roller 101 at a predetermined timing. The print sheet 108 is transferred while being sandwiched between the peripheral wall 104 deformed outwardly by being pressed by the inner roller 106 and the outer roller 101. During the time period, ink is transcribed onto the print sheet 108 by permeating from the perforated portion 105 through a perforated portion of the stencil sheet 107 to thereby carry out stencil printing.
However, the stencil sheet 107 is only wound around the outer peripheral face of the peripheral wall 104 and brought into contact therewith. Therefore, when the stencil sheet 107 is applied with pressure by being sandwiched between the inner roller 106 and the outer roller 101, as shown by FIG. 13, ink which has permeated through the perforated portion 105 of the peripheral wall 104 spreads to outer sides. Thereby, there has been a case in which ink leaked out from a gap between the nonperforated portion 109 of the peripheral wall 104 and the stencil sheet 107.
Hence, it is an object of the present invention to provide a stencil printing machine capable of preventing ink from leaking out from between a peripheral wall and a stencil sheet in order to resolve the above-described problem.
In order to achieve the above-described object, according to a first aspect of the present invention, there is provided a stencil printing machine comprising:
a printing drum 1 in a cylindrical shape having a peripheral wall 7 having an ink-nonpermeable nonperforated portion 123 around an ink-permeable perforated portion 121, wound with a perforated stencil sheet 127 on an outer peripheral face of the peripheral wall 7 and rotating around a central axis line of the printing drum 1 per se;
ink supplying means provided at inside of the printing drum 1 for supplying ink onto an inner peripheral face of the peripheral wall 7;
an inner roller 23 provided at the inside of the printing drum 1 in parallel with the printing drum 1 and brought into contact with the inner peripheral face of the peripheral wall 7 over the perforated portion 121 and the nonperforated portion 123; and
an outer roller 63 provided at outside of the printing drum 1 in parallel with the printing drum 1 and brought into contact with the outer peripheral face of the peripheral wall 7;
wherein a thickness t2 of the nonperforated portion 123 is formed to be thicker than a thickness t1 of the perforated portion 121 and the nonperforated portion 123 is projected to the inner peripheral face of the peripheral wall 7; and
wherein the nonperforated portion 123 is sandwiched between the inner roller 23 and the outer roller 63.
According to a second aspect of the present invention, there is provided the stencil printing machine in the stencil printing machine according to the first aspect:
wherein a portion of the nonperforated portion 123 formed to be thicker than the perforated portion 121 is constituted by a projected portion 125 provided on the nonperforated portion 123 on the side of the inner peripheral face of the peripheral wall 7; and
wherein the projected portion 125 is formed along both side edge portions of the perforated portion 121 in a direction of rotating the printing drum 1.
According to a third aspect of the present invention, there is provided the stencil printing machine in the stencil printing machine according to the first aspect:
wherein a portion of the nonperforated portion 123 formed to be thicker than the perforated portion 121 is constituted by a projected portion 125 provided on the nonperforated portion 123 on the side of the inner peripheral face of the peripheral wall 7; and
wherein the projected portion 125 is formed along both side edge portions and a rear side edge portion of the perforated portion 121 in a direction of rotating the printing drum 1.
According to a fourth aspect of the present invention, there is provided the stencil printing machine in the stencil printing machine according to the second aspect or the third aspect:
wherein the inner roller 23 is formed with recess portions 129 brought in mesh with the projected portions 125 and constituting recesses lower than a height of the projected portions 125 at portions of the inner roller 23 brought into contact with the projected portions 125 formed along the both side edge portions of the perforated portion 121.
According to a fifth aspect of the present invention, there is provided the stencil printing machine in the stencil printing machine according to the first aspect:
wherein the nonperforated portion 123 is constituted by coating an ink-nonpermeable material to a surrounding of the perforated portion 121 constituted by weaving flexible wire members in a shape of a net to constitute the perforated portion 121.
In printing operation, the inner roller 23 is lowered and is brought into contact with the inner peripheral face of the peripheral wall 7. The peripheral wall 7, the stencil sheet 127 and the print sheet P are sandwiched between the inner roller 23 and the outer roller 63. At this occasion, the nonperforated portion is thicker than the perforated portion 121 and accordingly, press force exerted to the peripheral wall 7 becomes higher at the nonperforated portion 123 than at the perforated portion 121. Ink which has permeated through the stencil sheet 127 is not moved to the side of the nonperforated portion 123 having larger pressure and is stopped on the side of the perforated portion 121 having smaller pressure.